CGI to domain name link

[#1]

Hi,
I have two domain names registered with plusnet. The first is a basic html website, and runs fine. I have changed the DNS settings to direct the second domain name traffic to a separate folder within the webspace without any problems.
I installed Mambo last night, following an excellent guide on the plus.net forum (http://usertools.plus.net/tutorials/id/55). Everything with Mambo works, I can access the website at ccgi.username.plus.com/site2/mambo/
I would like anyone typing in the second domain name URL to now see ccgi.username.plus.com/site2/mambo/
So type in www.secondwebsite.co.uk and they see the mambo site, with all the header bar addresses shown in the format www.secondwebsite.co.uk/whatever/ etc
I did find an article on the forum describing changes to the plusnet domain name settings > configure > specify DNS settings, but I'm not sure if this is what I'm after.
Can anyone shed some light on what I have to do?
Thanks!

[#2]

This is what I did to redirect my domain.tld to the subdirectory on ccgi:
http://portal.plus.net/central/forums/viewtopic.php?t=52576
From Joomla I guess that also Mambo might need for full functionality in the administrator panel to be set to the domain.tld and a .htaccess in a Mambo directory needs to be set to that as well (can't access the post - right now PlusNet put their page to "essential maintenance").

[#3]

Here it is, rather towards the end of the post. Actually it is about search machine friendly URLs - and I am not sure if that applies to Mambo:
http://portal.plus.net/central/forums/viewtopic.php?t=57146
Here in regards to Joomla:
http://portal.plus.net/central/forums/viewtopic.php?t=56592